.shadow {
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background-color: rgba(0, 0, 0, 0.4);
}

.center {
  width: 400px;
  background-color: #fff;
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  border-radius: 10px;
}

header {
  border-bottom: 1px solid #aaa;
  font-size: 20px;
  line-height: 30px;
  padding: 20px;
}

main {
  min-height: 100px;
  padding: 20px;
}

footer {
  height: 40px;
  border-top: 1px solid #aaa;
  padding: 20px;
  display: flex;
  justify-content: flex-end;
}
